Does your ovulation day vary?

My cycle is pretty consistent in that it’s 38 days long, and I ovulate on CD25. I started testing 48 hrs before my predicted ovulation but my opk tests were all negative. I also had no change in CM, which I normally do. I find it hard to believe I would’ve missed it due to the CM changes. So I’m wondering, could it be late? I tried googling about it but all I can find info on is consistent early or no ovulations... not much about a random fluke — which I’m hoping this is. Anyone else experience this? I’ve never had this happen since I started tracking everything. Thanks!